摘要
研究了少量甲基丙烯酸钠(NaMA)存在下单体极性对甲基丙烯酸甲酯(MMA)/丙烯酸丁酯(BA)无皂乳液共聚合的影响.单体极性降低,使粒径减小、聚合速率提高、乳液表面张力和粘度降低、粒子表面电荷密度增大、聚合物分子量提高.MMA/NaMA无皂乳液聚合物只呈现一个玻璃化温度Tg,BA/NaMA无皂乳液聚合物呈现两个Tg,MMA/BA比为2∶1~1∶2的MMA/BA/NaMA无皂乳液聚合物呈现四个Tg,这是由于粒子外面相对富含OSO-3和COO-基聚合物的亚层溶解了较多的水,使BA向粒子中心扩散,MMA向外扩散,造成组成差异和相分离而引起的.
The soapless emulsion copolymerization of methyl methacrylate (MMA) and n- butyl-acrylate (BA) with various ratios of MMA to BA in the presence of small amount of sodium methacrylate (NaMA) was studied.Increasing BA feed fraction results in a decrease of particle diameter,surface tension and viscosity of the latexes,and an increase of particle number,polymerization rate,surface charge density of the latexes and molecular weight of copolymer.The DSC thermogram of MMA/NaMA soapless latex copolymer (SLC) shows one glass transition temperature (Tg),while that of BA/NaMA SLC shows two Tg, and those of MMA/BA/NaMA SLCs with the ratio of MMA to BA within 2∶1~1∶2 show 4 Tg.The heterogeneity of copolymer composition for multiple Tg is ascribed to the assumption that the dissolved water in the sublayer surrounding the particle,enriched with —OSO_3^- and —COO^- groups,will cause the concentration gradients of MMA and BA monomers and phase separation.
出处
《高分子学报》
SCIE
CAS
CSCD
北大核心
1998年第2期208-213,共6页
Acta Polymerica Sinica
关键词
NAMA
MMA
BA
无皂乳液共聚
共聚
乳液共聚
Emulsifier free emulsion
Monomer polarity
Surface charge density
Molecular weight
Glass transition temperature